You could lift a picture of an old masters' painting of Mary nursing Jesus to put on your sign.
But I guess that'd be offensive on multiple fronts.
hmmmm they're offended that you put a "do not disturb" sign out; jealous that you can do that....
Maybe you should keep the cow and say "come on in, just fixing the baby's meals for tomorrow." Then you're not getting the privilege of shutting the world out
And they're welcome to see how fun it is to pump!
Or you could just make the offer and see how fast the fools scramble to fall all over themselves saying "do not disturb" is Fine.